In a concentrated period of three weeks during 2010 June, the STSS Demonstrator satellites were used to monitor three separate lests of ground-launched missiles. Two were from Vandenberg and one was from the Hawaiian islands. Several different orbital/trajectory scenarios were tested.

Three months later came another test that was observed by the satellites. A Minuteman III launch from Vandenberg was planned for September 15. A delay in preparation meant that it had to be postponed two days, to September 17, in order for the STSS Demonstrators to be back in a position to observe it.

Coincident with the September 17 test, Northrop Grumman revealed that, on July 19, one of the two satellites had tracked a NOAA weather satellite in space. Later, the company issued a list of milestones that the satellites had achieved and added to the list of already-known events - notes on it can be found under "Detection Test Calendar" in the left-hand menu.

2010 June - How the News Unfolded

From the Zarya point of view, the first indication that a test had occurred was when "Jonathan's Space Report" turned up in the in-box on July 17. It included, among other launches, Jun 29 as the date of a missile test from Hawaii. Looking at the positions of the STSS Demonstrator satellites showed them to be straddling the launch site.

Simultaneously with an analysis being published to the Zarya web site on July 20, the Space Daily news web site ran a story saying that a missile test on Jun 16 had also been monitored. Further searching on the web turned up a Northrop-Grumman press release covering the Jun 29 event that also mentioned the Jun 6 launch and stated that three events had been monitored in total.

There is a link in the left menu to notes about each of the tests - June 6, June 16, June 29 and a further one that took place September 17.

Detection Scenarios

Open literature on the functioning of STSS talks of two scenarios under which events can be monitored.

In the first, described as "above the horizon", the missile is seen against the background of space as it rises above the Earth's limb. There are two variants of this depending whether or not the limb is illuminated. If it is, then the contrast between the target and the background will be reduced while the missile is within the atmosphere and there will be glare until the Earth moves out of view of the sensor.

The second scenario is "below the horizon" where the satellite is looking down the launch and, again, the Earth might, or might not be in sunlight. This setup should not be confused with the alternative meaning of "below the horizon" where it means something is out of sight because the Earth is blocking the view.

Both scenarios were represented in the STSS Demonstrator tests and targets were observed as the moved from one scenario to the other.

Jun 6 Event

This being the first test may explain in part why the satellites were above the American continent. They were well within the view of ground stations throughout the crucial period. More details, including a map, can be found here or from the left hand menu.

Satellite

Scenario

STSS Demo 1 (USA 208)

target below horizon - bright background

STSS Demo 2 (USA 209)

target above horizon - illuminated limb

Jun 26 Event

Depending on the apogee reached by the missile in the cruise phase of its flight, it may have passed beneath SV-1. In that case, part of the mid-course flight of the missile could have been a below-horizon event. More details, including a map, can be found here or from the left hand menu.

Satellite

Scenario

STSS Demo 1 (USA 208)

target above horizon - dark limb

STSS Demo 2 (USA 209)

target above horizon - dark limb

Jun 29 Event

In this case, at the moment of launch the target was in the centre of the overlapping viewing area between the two satellites and in the center of the stereoscopic viewing area. The THAAD interceptor would also have been visible and detectable. More details, including a map, can be found here or from the left hand menu.

Satellite

Scenario

STSS Demo 1 (USA 208)

target below horizon - dark background

STSS Demo 2 (USA 209)

target below horizon - dark background

In all three cases, the related STSS-ATRR (Space Tracking and Surveillance System - Advanced Technology Risk Reduction) satellite was nearby and had a view of some, if not all, of each event.

Acknowledgement

This analysis would not have been possible without the work by members of the Seesat-L online visual satellite observing group and the elements files for classified objects published daily by Mike McCants.

The observational and subsequent analysis work to produce the element sets used to generate the maps is gratefully acknowledged as is the existence of the satellite tracking computer program Orbitron, written by Sebastian Stoff.